The present invention relates to endless transmission belts and, in particular, to endless transmission belts for use in continuously variable transmissions of the chain type in which a number of link plates are interconnected in an endless manner.
A conventional endless belt for use in continuously variable transmissions of the above-mentioned type is shown in FIGS. 1 through 4.
The conventional endless transmission belt 1, shown in FIGS. 1 through 4 includes a plurality of link plates 2 which are interconnected by a plurality of pins, thereby forming sets 5 of the link plates 2, and first and second blocks 6 and 7 which are mounted on the sets 5. Each of the link plates 2 has pin holes 2a and 2b formed therein at its two ends. Pairs 3 of pins are passed through the pin holes 2a and 2b, thereby alternately interconnecting the link plates 2.
As shown in FIG. 4, each pair of pins 3 comprises paired pins 3a and 3b having contact surfaces P1 on which the pins 3a and 3b come into mutual rolling contact. The pins 3a and 3b are passed through the pin holes 2a and 2b, with their contact surfaces P1 facing each other. As shown in FIGS. 2 and 3, each pair 3 of pins has a length greater than the width of the sets 5 of the link plates 2 by a predetermined dimension.
Each of the first and second blocks 6 and 7 has an opening portion 6b and 7b respectively through which the sets 5 of link plates 2 are passed, and tapered surfaces 6c or 7c formed on the left and right sides of the block as viewed in FIG. 1 and adapted to come into contact with the pulleys. Pin engagement grooves 6a or 7a for receiving the pairs 3 of pins are formed in the contacting surfaces of the first and second blocks 6 and 7.
Further, retainer engagement grooves 6e and 7e are formed on the left and right sides of each of the first and second blocks 6 and 7 respectively. Retainers 9 are received in the facing pairs retainer engagement grooves 6e and 7e to retain the pairs 3 of pins in place.
The above-described endless transmission belt is advantageous in that the pins are positively engaged with the link plates, and V-blocks are positively engaged with the pins while they can smoothly rotate relative to the pins, thereby enabling great improvements in durability and torque transmission capacity to be achieved.
An endless transmission belt of the type described above, however, has the following disadvantages. As shown in FIGS. 5 (a) and (b), when the belt is fitted around the pulleys, since a large number of segments, each corresponding to the length of the chain pitch, are positioned in the circular arc determined by the rotational radius of the belt, the belt experiences speed variations, vibration, and generation of noise (polygon effect). In FIGS. 5 (a) and (b), symbols Vx, r, .omega., V'x, and .theta. represent the speed of the belt in the circumferential direction, the radius of the bent portion of the belt, the angular velocity, the horizontal component of the circumferential speed, and the angle of rotation, respectively.
In addition, when the pins 3a and 3b come into a portion of the belt curved around a pulley, the point of their mutual rolling contact may be displaced, the pins 3a and 3b per se is displaced in the radial direction, and the relative position of the pins 3a and 3b and the blocks 6 and 7 may be changed due to the rotation of these members relative to one another, thereby resulting in an increased degree of variation in the belt speed, vibration, and noise.